There is known a method for the direct covalent bonding of biologically active molecules to chemically modified polyamides, such as various types of nylon (nylon 6, nylon 66). The known method involves a 4 -component condensation reaction of an amine, a carboxyl moiety, an aldehyde, and an isocyanide: generally the polymeric carrier provides the isocyanide moieties, and the protein the amine or the carboxyl moieties, an aldehyde and the forth component being added to the reaction mixture. It is one of the drawbacks of this known method that the biological activity of certain compounds is impaired by the aldehyde.